2.3 Astro 1 - Astro 1 Section 1 Professor Brandt Wednesday...

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Astro 1 Section 1 Professor Brandt Wednesday February 3rd 1999 Announcements: Lecture notes: Class 11 Nuclear fusion powers the sun. H -> He Only occurs in the core (very center) of the sun Core has T of about 14-15 million degrees very hot - > makes short wavelength radiation In fact the core of the sun is so hot it makes x and gamma rays as the main type of radiation - these are the shortest wavelength radiation. Now x/gamma rays are harmful to people - so if x/gamma rays are made in huge amounts in the core of the sun then why don't they kill us? To understand we will follow the path of a single gamma ray from creation in the core to escape from the solar surface. We shall see that it's not a direct route but takes long and twisting route to escape as the gamma ray leaves the core it passes into the radiation zone. This is a layer of gas above the core made of H and He. There is no nuclear burning here and a it has a temperature of about 4x10 6 K Great deal of matter here that gamma rays must pass through. Photons interact with matter via absorption and re-emission. When absorbed and re-emitted it has a new energy corresponding to region where emitted - lower T so lower E. So energy is stolen away from a gamma ray photon via this process of absorption and re-emission.
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  • Spring '99
  • Brandt
  • Astronomy, Gamma ray, Little Ice Age, low density, solar surface, x/gamma rays

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